/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.solr.internal.csv;

import java.io.StringWriter;
import java.io.StringReader;
import java.io.IOException;

/**
 * Utility methods for dealing with CSV files
 */
public class CSVUtils {

	private static final String[] EMPTY_STRING_ARRAY = new String[0];
	private static final String[][] EMPTY_DOUBLE_STRING_ARRAY = new String[0][0];

	/**
	 * <p>
	 * <code>CSVUtils</code> instances should NOT be constructed in standard
	 * programming.
	 * 
	 * <p>
	 * This constructor is public to permit tools that require a JavaBean
	 * instance to operate.
	 * </p>
	 */
	public CSVUtils() {
	}

	/**
	 * Converts an array of string values into a single CSV line. All
	 * <code>null</code> values are converted to the string <code>"null"</code>,
	 * all strings equal to <code>"null"</code> will additionally get quotes
	 * around.
	 * 
	 * @param values
	 *            the value array
	 * @return the CSV string, will be an empty string if the length of the
	 *         value array is 0
	 */
	public static String printLine(String[] values, CSVStrategy strategy) {
		// set up a CSVUtils
		StringWriter stringWriter = new StringWriter();
		CSVPrinter csvPrinter = new CSVPrinter(stringWriter, strategy);

		// check for null values an "null" as strings and convert them
		// into the strings "null" and "\"null\""
		for (int i = 0; i < values.length; i++) {
			if (values[i] == null) {
				values[i] = "null";
			} else if (values[i].equals("null")) {
				values[i] = "\"null\"";
			}
		}

		// convert to CSV
		try {
			csvPrinter.println(values);
		} catch (IOException e) {
			// should not happen with StringWriter
		}
		// as the resulting string has \r\n at the end, we will trim that away
		return stringWriter.toString().trim();
	}

	// ======================================================
	// static parsers
	// ======================================================

	/**
	 * Parses the given String according to the default {@link CSVStrategy}.
	 * 
	 * @param s
	 *            CSV String to be parsed.
	 * @return parsed String matrix (which is never null)
	 * @throws IOException
	 *             in case of error
	 */
	public static String[][] parse(String s) throws IOException {
		if (s == null) {
			throw new IllegalArgumentException("Null argument not allowed.");
		}
		String[][] result = (new CSVParser(new StringReader(s))).getAllValues();
		if (result == null) {
			// since CSVStrategy ignores empty lines an empty array is returned
			// (i.e. not "result = new String[][] {{""}};")
			result = EMPTY_DOUBLE_STRING_ARRAY;
		}
		return result;
	}

	/**
	 * Parses the first line only according to the default {@link CSVStrategy}.
	 * 
	 * Parsing empty string will be handled as valid records containing zero
	 * elements, so the following property holds: parseLine("").length == 0.
	 * 
	 * @param s
	 *            CSV String to be parsed.
	 * @return parsed String vector (which is never null)
	 * @throws IOException
	 *             in case of error
	 */
	public static String[] parseLine(String s) throws IOException {
		if (s == null) {
			throw new IllegalArgumentException("Null argument not allowed.");
		}
		// uh,jh: make sure that parseLine("").length == 0
		if (s.length() == 0) {
			return EMPTY_STRING_ARRAY;
		}
		return (new CSVParser(new StringReader(s))).getLine();
	}

}
